Homogenizer



Sept. 1,1970 M. w. CHURCH, JR

HOMOGENIZER 2 Sheets-Sheet 1 Filed Jan.

WM. M @im mm m Y v v/5u 4%/ C Vm lNvENToR l j Merton W. hurchkdr.

- AUQRNEY M. w. CHURCH, JR

` Sept. 1, 1970 HOMOGENIZER Filed Jan. s, 19e? 2 Sheets-Sheet 2 4 INVENTOR Merton W. Church, Jr. MMM

ATTORNEY United States Patent 3,526,391 HOMOGENIZER Merton W. Church, Jr., Trenton, Mich., assignor to Wyandotte Chemicals Corporation, Wyandotte, Mich., a corporation of Michigan Filed Jan. 3, 1967, Ser. No. 606,696 Int. Cl. B01f 13/.00

U.S. Cl. 259-4 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the homogenizing of liquids and, more particularly, to an apparatus for dispersing a substance in a liquid which comprises a housing having a chamber, an inlet and an outlet defined therein, and a series of orifice plates arranged in succession in the chamber. Each plate has a sharp edge orifice extending through it with the orifice of one plate being out of alignment with the orifice of the next succeeding plate whereby a stream of fluid discharging through the orifice of one plate impinges against an impervious surface. Thus, the stream of fluid is forced to change direction of travel to pass through the orifice in the next succeeding plate.

It is well known in the prior art to homogenize liquids by forcing them under pressure through narrow restrictions or the like or by the rapid movement of mechanical parts or combinations of both. It is particularly well known in the prior art to employ for this purpose devices in a form in which the liquid is forced between closely opposed surfaces to cause the liquid to flow in thin films or very narrow streams of changing direction. These prior art devices employ long wall-type or square-edged orifices. Such devices have certain inherent disadvantages due to the fact that enormous liquid pressures are generally required to force the liquid through these devices, coupled with the fact that the globules of the material to be dispersed in the liquid are often merely flattened out rather than disrupted. Further, devices of this type are diflicult to manufacture due to the machining required for the orifices and passageways and they are often difficult to clean.

Accordingly, it is a purpose of this invention to provide an apparatus of this character which will embody in the apparatus no moving parts, which will form dis persions of relatively small particle size and a high degree of uniformity, and which will not require excessively high pressures to force the liquid through the device. This invention will be more fully understood from the following description illustrating several preferred embodiments of the invention when considered in connection with the drawings wherein:

FIG. l is a cross sectional view of an emulsifying device embodying the principles of this invention;

FIG. 2 is a cross sectional view of an embodiment of an emulsifying device similar to that of FIG. l employing a larger number of orifice plates than the embodiment of FIG. 1;

FIG. 3 is a cross sectional View of the emulsifying device of FIG. l taken along the line 3 3 of FIG. l;

FIG. 4 is a view of a modified orifice plate of the device of FIG. l viewed in the same direction as section 3 3 of FIG. 1;

FIG. 5 is a cross sectional view of an additional ernbodiment of the emulsi-fying device of this invention;

FIG. 6 is a cross sectional view of the emulsifyng device of FIG. 5 taken along the line 6 6 of FIG. 5;

FIG. 7 is a cross sectional view of a further embodirnent of the emulsifying device of this invention; and

FIG. 8 is a cross sectional view of the emulsifying 3,526,391 Patented Sept. 1, 1970 device of FIG. 7 taken along the line 8 8 of FIG. 7.

With reference now, more particularly, to FIG. 1 of the drawings, it will be seen that the device embodying the principles of this invention comprises a housing 1 having a chamber 2, an inlet 3 and an outlet 5 defined therein, and a series of plates 4 arranged in succession in chamber 2 having orifices 6 extending therethrough. Housing 1 comprises two separable parts, viz., a hollow body 7 having outlet 5 and chamber Z defined therein and an inlet member 9 having inlet 3 defined therein. Inlet member 9 is threaded into the end of body 7 opposite the outlet 5 into engagement with the end plate of the series of plates 4 `by means of matching external threads 11 on inlet member 9 and internal threads 13 in body 7.

While three plates are shown in FIG. 1, a larger number may be employe-d for liquids which are more diflicult to emulsify. For example, the embodiment of FIG. 2 which is otherwise identical to the embodiment of FIG. l illustrates the use of nine plates 4. Since with the exception of the number of plates, the embodiment of FIG. 2 is identical to that of FIG. 1, the description of FIG. 1 applies equally to FIG. 2 with the exception of the number of plates. Accordingly, identical numerals are applied to each figure. In general, the fewer the number of plates 4 employed the less the pressure required to force liquid through the device. Accordingly, the fewest number of plates which will do a satisfactory homogenizing job is lpreferred and will vary depending upon the particle size desired, particle size distribution, the properties of the material to be homogenized or dispersed and the pressure employed. In general, the number of plates will be greater than l and less than 20.

The plate 4 at the outlet end of the body 7 rests against a shoulder 22 defined in body 7. The inlet member 9 which is threaded into body 7 engages the end plate 4 whereby the plates 4 are held in contact. These plates are provided with finished contacting surfaces to prevent flow of fluid between same. To prevent flow of fluid around the plates 4, O rings 24 which engage the inner surface of chamber 2 are provided in recesses 26 around the periphery of plates 4.

Each plate 4 is provided with at least one orifice 6 extending therethrough and may have more than one orifice 6. The orifices may be round, however, elongated orifices such as illustrated by the numerals 6 and 6" in FIGS. 3 and 4 are preferred. Orifices of the type indicated in FIGS. 3 and 4 by the numerals 6 and 6 which are elongated in a direction transverse to the direction of flow of a fluid passing through the orifice are nearly as,

effective in dispersing the material as a round orifice and permit a greater rate of fluid flow, thus requiring less pressure to force the fluid through the apparatus. The smallest orifice dimension in a direction transverse to the fluid flow generally ranges from about IAO() to 1A the diameter of the inlet 3. The longest dimension is limited only by the boundaries of the orifice plate 4. The orifice is preferably a sharp edge orifice to reduce resistance to fluid flow to a minimum without reducing homogenizing effectiveness. As used herein, the expression sharp edge orifice means either an orifice with tapered sides or one where any parallel sides are of a very short length and particularly are less than the smallest orifice dimension in a direction transverse to the fluid flow as shown in FIG. l.

IEach orifice 6 of each plate 4 is out of alignment with any orifice of the previous plate and the next succeeding plate whereby the stream discharging through the orifice of a preceding plate 4 impinges against an impervious surface 32. This produces eddy currents in the stream of fluid which also is forced to change direction to pass through the orifice of the next succeeding plate 4 due to the fact that the orifices are out of alignment with each other. To minimize resistance to fluid flow in the embodiments of FIGS. 1-4, i.e., embodiments where impingement surface 32 is a fiat surface, the distance, i,e., width of space 34, between the orifice discharge and the irnpingement surface 32 of the next succeeding plate is at least about 11/2 times the smallest orifice dimension in a direction transverse to the fluid flow. This reduces the resistance to fiow of the fluid through the apparatus whereby the high pressures heretofore necessary to produce a perfect homogenizing or dispersing action are not required and, in fact, relatively low pressures may be employed even with an embodiment such as FIG. 2 employing a large number of plates 4 making this apparatus superior to prior devices which generally employ very restricted grooves and passages. In order to have effective homogenization or dispersion, the width of space 34 should not be greater than about 14. the diameter of inlet 3.

The impact of the stream from each orifice on the impingement surface 32 in combination with the eddy currents produced thereby and the change in direction of flow result in a high degree of homogenzation or dispersion equivalent to that obtained with highly restricted passageways and yet permits the use of comparatively large passageways, i.e., the space 34 between the discharge of the orifice `6 and the impingement surface 32.

The inlet and outlet ends of the housing 1 are provided with suitable means for coupling to pipe or other conduit means to provide for inlet and discharge of the fluid being homogenized. One means for accomplishing this is to provide the outer ends of body 7 and inlet member 9 with externally threaded coupling portions 36 and 38, which may be of well-known form. Coupling portions 36 and 38 when employed in connection with conventional pipe couplings or union-type couplings well known to those skilled in the art provide a liquid pressure-tight conduit connection for conduit communication with the chamber 2 and plates 4.

In general, devices of this type require frequent cleaning which is often very difficult and time consuming. However, the apparatus of the instant invention has less tendency to deposit materials inside the device and, therefore, less frequent cleaning is required. Further, when cleaning s required it is only necessary to uncouple the device at coupling portions 36 and 38, then unscrew the two parts 7 and 9 from each other whereupon the plates 4 may be easily removed for cleaning.

This invention is susceptible of various modifications and is not limited to the exact construction illustrated and described in FIGS. l, 2, 3, and 4. Additional embodiments of this invention which are particularly preferred are illustrated in FIGS. and 6 and FIGS. 7 and 8. With reference more particularly to FIG. 5, it will be seen that the device of this embodiment, as in the embodiment of FIGS. 1 and 2, comprises a housing 1 having a chamber 2, an inlet 3 and an outlet 5, a hollow body member 7 and an inlet member 9 which is threaded into the hollow body member 7 by means of threads 11 and 13. Suitable coupling means for coupling the device in a conduit such as coupling portions 36 and 38 similar to those of the em- Ibodiment of FIGS. 1 and 2 are also provided.

The principal distinction between the embodiment of FIG. 5 and that of FIGS. 1 and 2 lies in the contour of the impingement surface. In the embodiment of FIGS. 1 and 2, the impingement surface 32 is a fiat surface which is formed by a portion of the plate 4 which does not have an orifice. In the embodiment of FIG. 5, a specially designed impingement surface 42 or 44 is provided which takes the form of a projection having side surfaces which converge upon each other. The impingement surface may have straight converging sides as seen in cross section as illustrated at 44 or may have concave converging sides as seen in cross section as illustrated at 42. Impingement surfaces 44 and 42 may be conical or modified, conical having concave converging sides as the case may be or in a preferred embodiment they may be essentially wedge shape as shown by reference also to FIG. 6. The device may employ all surfaces of the type of 44, or all surfaces of the type 42, or both may be employed together in an arrangement such as that shown in FIG. 5. In the embodiment shown in FIG. 5, the orifice plate 46 is provided as a web in an otherwise hollow cylinder 48 which replaces the plates 4 of FIGS. 1 and 2. The impingement surface 44 or 42 may be provided within the cylinder 48 by any suitable mounting means. For example, it may be a portion of a block 51 of metal or other suitable material fiattened at the end portions 49 which extend -beyond the hollow cavity 50 of each cylinder 48. Suitable recesses 52 matching the end portions 49 of the block 51 may be provided in the sides of the cylinder 48 to permit insertion of the end portions 49 of the block 51 as shown more clearly in FIG. 6.

The fiuid flows from right to left through the apparatus an-d passes through each orifice 40 defined within each plate 46 and impinges on the succeeding impingement surface 44 or 42 which necessitates a change in the direction of fiow of the fluid before fiowing through the next succeeding orifice. impingement on the surfaces 44 or 42 results in eddy currents in the stream of fluid to bring about substantial homogenization. For most fluids or systems the embodiments of FIG. 5 and FIG. 7 are preferred since the surface 44 and particularly the surface 42 provide a controlled change of direction to provide eddy currents having an optimum effect in homogenizing or dispersing materials in the fiuid. The effect particularly of the surface 42 is in effect akin t0 centrifugal force tending to increase the effect of the impingement and also cause the material to reverse flow and impinge on the orifice plate 46, doubling the effectiveness of the impingement and the eddy currents. However, as in the embodiment of FIGS, 1 and 2, a substantial space for fluid fiow is employed whereby the resistance to fiuid fiow is considerably less than in prior art devices for a given amount of homogenization or dispersion.

As in the embodiments of FIGS. 1 and 2, the cylinders 48 are provided with O rings 54 which are provided in grooves or recesses S6 to prevent fluid fiowing around the cylinders 48 and orifices 40, etc. Like the embodiments of FIGS. 1 and 2, this device does not require frequent cleaning and when cleaning is required it may be disassembled very easily in the same manner as the embodiments of FIGS. 1 and 2. In the embodiment shown in FIG. 6, the orifice 40` is elongated to match the wedge shape of impingement surface 42. Such elongated orifice 40 is preferred for use 'with a wedge shape impingement surface 44 or 42 as shown in FIG. 6 whereas a round orifice is preferred for use with a conical impingement surface 44 or 42. The Wedge shape impingement surface 42 or 44 and elongated orifice combination is preferred since it permits a greater amount of fiuid flow without a corresponding reduction in homogenizing effect.

The embodiment of FIGS. 7 and 8 operates on substantially the same principle as that of FIGS. 5 and 6 and has substantially the same advantages. The principal difference lies in the fact that the orifices are not in line with each other but staggered in a manner similar to the embodiments of FIGS. 1 and 2. The housing 1, chamber 2, inlet 3, outlet 5, hollow body 7, inlet member 9, threads 11 and 13, as well as the coupling portions 36 and 38, all function in the same manner as in the embodiments of FIGS. 1 through 6. Accordingly, these will not be described in detail. Similar to the embodiment of FIG. 5 the orifices and impingement surfaces in this embodiment are provided in cylindrical members which are also provided with grooves 67 and O rings 69 to function in the same manner as grooves and O- rings 56 and 54 of FIG. 5. The cylindrical members 65 are provided with hollowed out chambers 71 on the upstream side of the cylinders. Nearly one-half of each chamber 71 has a partially spherical surface on the downstream side of the chamber with orifices 73 cut through the wall of the cylinder into the spherical portion of the chamber.

As in the previously described embodiments of this invention, elongated orifices 73 such as shown in combination with FIG. 8 are preferred although round ones may be employed. impingement surfaces 75 or 77, substantially the same as 42 and 45 of FIGS. 5 and 6, are provided in the cylinders 65 just opposite the orifice 73 of the preceding cylinder. These surfaces may be conical Where the orifices are round or they may be wedge shape where the orifice is elongated, all as described above with respect to the embodiments of FIGS. and 6. The surfaces 75 and 77 may be machined directly out of the cylinder 65 or as shown they may be in the form of inserts 79 and 81. In the embodiment as shown in FIG. 8, the inserts 79 would be rectangular and would be provided in an appropriate matching opening in the Iwall of the cylindrical member 165. The impingement surfaces 75 and 77 in this embodiment function in substantially the same manner as surfaces 42 and 44 of FIG. 5 and thus will not be described further. As in the embodiments of FIGS. 1 4, the embodiments of FIGS. 5-8 require that the distance between the orifice discharge and the impingement surfaces 42, 44, 75 or 77, at its closest point, should not be greater than 1/2 the diameter of inlet 3. The closest point or edge of impingement surface 42, 44, 75 or 77 may be as close as possible to the orifice discharge and, accordingly, for the embodiments of FIGS. 5-8 there is no minimum distance between the orifice discharge and the impingement surface at its closest point or edge.

The apparatus of this invention may be used for performing any processes on liquids such as homogenizing, dispersing, emulsifying, viscolizing, etc.

Applicant has found that the device of this invention is particularly useful for the production of aqueous dispersions of polyurethane polymers characterized by high mechanical stability. The preparation of polyurethanes is disclosed in many references including the texts entitled Polyurethanes by Bernard A. Dombrow, published by -Reinhold Printing Corporation, New York, N.Y., 1957, and Polyurethanes: Chemistry and Technology of I. H. Saunders and K. C. Frisch, published by Interscience Publishers, New York- London, wherein disclosure is made of methods for producing polyurethanes including those wherein an isocyanate terminated prepolymer is first prepared and then reacted with a chain extending agent.

Aqueous dispersions of polyurethane polymers are desirable as an impregnant for paper to increase burst strength and fold resistance, as coatings for boxboard to increase abrasion resistance, as coatings for textiles to provide Waterproof fabric which is light in |weight and which retains a high degree of flexibility and wear resistance, as coatings for leather, as a material to make elastic or plastic foams, for elastic fibers by latex coagulating processes, for the preparation of articles by dipping processes and for casting on a at surface to form high strength films useful for packaging and other protective coatings.

The apparatus of the present invention may be used to prepare aqueous dispersions of polyurethane polymers by mixing (I) an isocyanate terminated polyurethane polymer formed from (a) active hydrogen containing organic compounds and mixtures thereof, and (b) an organic polyisocyanate with Water and dispersing the polymer in the water with the apparatus of this invention as described above.

A chain extender (II) containing active hydrogen is then added to the water dispersion of polymer (I) with rapid agitation.

The isocyanate terminated polyurethane polymer (I), also referred to as a prepolymer, employed as a starting material may be any such type compound which may be obtained by the reaction of a selected active hydrogen containing compound (a having an average molecular weight of at least about 300 with a stoichiometric excess of an organic polyisocyanate (b). Such prepolymers are capable of molecular weight increase through chain extension with chain extension agents.

In general, any organic compound containing at least two active hydrogen atoms may be reacted with a stoichiometric excess of an organic polyisocyanate to get a prepolymer or an initial addition product which is then capable of a molecular weight increase through chain extension with a chain extender. Active hydrogen containing compounds of this sort include the polyalkylene ether glycols, the poly(alkylene ether-alkylene thioether) glycols, polyalkylene esters of alkylene diacids, polyalkylene esters of arylene diacids, esters of polyhydric alcohols and hydroxy fatty acids, alkyd resins containing hydroxyl or carboxyl end groups and polyester amide resins. The term active hydrogen atoms refers to hydrogens which, because of their position in the molecule, display activity according to the Zerewitinoff test as described by Kohler in J. Am. Chem. Soc. 49, 3181 (1927). Linear compounds containing hydrocarbon groups linked together by ether or ester linkages and having terminal hydroxyl groups are preferred representatives of this type of compound. A particularly useful class of active hydrogen containing compounds for this purpose is the polyalkylene ether glycol which have the general formula H(OR)nOH where R is an alkylene radical and n is an integer which in a preferred embodiment is sufficiently large that the compound as a whole has a molecular weight of at least about 300. Molecular weights of up to 10,000 are satisfactory. Polyethylene ether glycols, poly-1,2-propylene ether glycol, polytetramethylene ether glycol, poly-1,2-dimethylene ether glycol, and polydecamethylene ether glycols are typical members of this class. Not all of the alkylene radicals present need to be the same. Glycols containing a mixture of radicals as in the compound HO(CH2OC2H4O)H, or HO(C2H4O)n(C3H6O)m(C2H4O)nH wherein n and mi are together sufficient for attainment of the desired molecular weight can be used. Polyethylene ether-polypropylene ether glycols, having the above-indicated formula, are among the preferred glycols.

Any of a wide variety of organic polyisocyanates (b) may be employed in the reaction, including aromatic, aliphatic and cycloaliphatic diisocyanates and combinations of these types. Representative compounds include aromatic diisocyanates, such as 2,4-tolylene diisocyanate, mixtures thereof with 2,6-tolylene diisocyanate usually in proportions of of the 2,4 isomer and 20% of the 2,6 isomer and referred to herein as mixed isomers of tolylene diisocyanate 80/ 20 2,4/ 2,6

Addition polyisocyanates which may be employed, for example, include: P,p'diphenylrnethane diisocyanate, 3,3'dimethyl-4,4'biphenylene diisocyanate, 3,3dimeth oxy4,4biphenylene diisocyanate, 3,3'diphenyl4,4'bi phenylene diisocyanate, 4chlorol,3phenylene diisocyanate, 3,3'-dichloro-4,4'biphenylene diisocyanate, and 1,5-naphthalene diisocyanate, and other polyisocyanates in a blocked or semi-inactive form such as the bis-phenylcarbamates of tolylene diisocyanate, p,p'diphenyl methane diisocyanate, p-phenylene diisocyanate, and 1,5- naphthalene and 1,S-tetrahydronaphthalene diisocyanate.

-In the preparation of the starting polyurethane polymer (I), an excess of the organic polyisocyanate (b) over the active hydrogen containing compound (a) is used. The ratio of organic polyisocyanate compound (b) to active hydrogen containing compound (a) is preferably such that the NCO/OH ratio is greater than about 1.3:1. While there is no upper limit to the NCO/ OH ratio for practical purposes a ratio greater than about 2.75 :1 is seldom employed.

The reaction may be eEected in the absence of a solvent When the-prepolymer (I) is a fluid at processing temperatures. When it is not or when it is desired to employ a solvent, convenient solvents are inert organic solvents having a boiling range above about 100 C. when the reaction is to be carried out in open equipment.

The solvents to be used are preferably those in which the reactants have some solubility but in which the nal chain-extended elastomer is insoluble. Ketones, tertiary alcohols and esters may be used.

Toluene and isopropyl acetate are preferred solvents. The amount of solvent used may be varied widely. Any amount of solvent up to about 100 parts of solvent per 100 parts of prepolymer has been found to be operable. The excess solvent, where large amounts are employed, may be separated partially or completely from the polymer prior to emulsication in the water solution. Sometimes the excess solvent is useful and is allowed to remain during the emulsifcation stage.

The active hydrogen containing compound and the isocyanate are ordinarily reacted by lheating with agitation at a temperature of about 50 to 130 C. without a catalyst or at about 25 to 60 C. Where a catalyst such as stannous octoate is employed. The reactants are heated for a period sufficient to react most, if not all, of the hydroxy groups, whereafter the prepolymer is allowed to stand and the free NCO content determined. A period of from about 1 to 4 hours is preferred when a catalyst is not employed whereas a period of from about minutes to 3 hours is preferred when a catalyst is employed.

Usual pHs are employed during preparation of the prepolymer, the reaction preferably being maintained substantially neutral. Bases accelerate the reaction, acids retard the reaction, and preferably neither are added.

The chain extending agent which is used in this irlvention is a compound containing a plurality of active hydrogen atoms capable of reacting with isocyanates. In the chain extenders useful in this invention, the active hydrogen atoms are preferably attached to oxygen, nitrogen or sulfur. The groups containing the active hydrogen will ordinarily be -OH, -SI-I, -NH-, -NH2, -COOH, -CONH2, -CONHR where R represents an organic radical, OZOH, SOzNHz, or -CSNH2. The chain extending compound may be aliphatic, aromatic or cycloaliphatic or of mixed type. Typical of many organic compounds which are useful in this connection are ethylene glycol, hexamethylene glycol, diethylene glycol, adipic acid, terephthalic acid, adipamid, 1,2-ethanedithiol, hydroquinine, monoethanolamine, 4-aminobenzoic acid, mphenylenediamine propylenediamine, 4-aminobenzamide, sulfanilamide, aminopropionic acid, l,4-cyclohexanedisulfonamide, 1,3- propanedisufonamide, 4-hydroxybenzoic acid, p-aminophenol, ethylenediamine, succinic acid, succinamide, 1,4- butanedisulfonamide, 2,4-tolylenediamine, bis(4amino phenyl)methane, beta-hydroxypropionic acid and 1,2- ethanedisulfonic acid. Compounds containing at least one amino group are preferred organic chain extending agents.

Certain of the chain extending agents are considerably more reactive with isocyanates than others and the speed of reaction may be, to some extent, controlled by a suitable choice of extending agent. The amines are particularly reactive agents. Particularly desirable for this purpose are diamines. Suitable diamines for carrying out the present process are inter alia aliphatic, cycloaliphatic, aromatic, araliphatic and heterocyclic diamines.

The amount of water to be employed in the formation of the dispersion is not critical, although, in general, the minimum amount will be equal to the volume of the initial addition product of the solvent solution or slurry of this product. When too small an amount of Water is employed, emulsions are obtained which are too thick to handle readily; while, on the other hand, dispersions which are too dilute are uneconomical to handle due to their excessive volume. In general, it is preferred to employ a proportion by weight of polymer (I) to Water of from about 1:4 to 2:1.

An emulsifying agent is often desirable although it is not always necessary. Any emulsifying agent or surface active agent which will give oil-in-water emulsions is satisfactory for use in the present invention. Satisfactory types of emulsifying agents are the polyethylene glycol ethers of long chain alcohols; quaternary ammonium salts; the tertiary amine or alkylol amine salts of long chain alkyl acid sulfate esters, alkyl sulfonic acids or alkyl aryl sulfonic acids; and alkali metal salts of high molecular weight organic acids. Nonionic agents are preferred when polymers containing ester groups are emulsied. The pH can then be regulated to a neutral value, preferably not above 7, to minimize any tendency toward hydrolysis. Salts of the high molecular weight organic acids may :be used as emulsifying agents. One method of incorporating such salts is to mix the acid, e.g., tall oil, with the prepolymei mass and to have the requisite amount of alkali present in the aqueous bath so as to form the emulsier in situ. Although there is presumably some reaction between the acid and the free isocyanate groups in the prepolymer, this is not significant if the mixture is fairly promptly added to the aqueous bath. From about 2% to 6% of the emulsifying agent based on the weight of the prepolymer employed will usually be found suicient to produce stable emulsions.

The amount of chain extender (II) should be suicient to react with all the free isocyanate groups in polymer (I). For practical purposes the chain extender (I-I) is preferably employed in amounts to provide an active hydrogen/NGO ratio of from about 0.7511 to l.9:1.

In a preferred embodiment of this invention, the chain extender (II) is dissolved in Water first, with or without an emulsifying agent, and agitated as needed. The mixture is added to the dispersion of the prepolymer (I) in water. The amount of `water to be employed is not critical. The over-al1 mixture is then dispersed by agitation.

The following examples are given to illustrate the invention:

EXAMPLE I (a) Prepolymer formation 1,000 grams of polyoxypropylene glycol of molecular weight averaging 1,000 are added to 348 grams of mixed isomers of tolylene diisocyanate (/20:2,4/2,6). The NCO/OH mole ratio is 2:1. The mixture is heated at C. for 3 hours.

(b) Chain extension 1,000 grams of the prepolymer are dissolved in 300 grams of toluene. This mixture along with 740 grams of aqueous surface active agent solution containing 5.4% by weight of the surface active agent consisting of dihydric polyoxyethylene-polyoxypropylenes having a molecular weight of about 16,000, a molecular weight of the polyoxypropylene base of about 3,250 and a polyoxyethylene content of about 80% by weight is pre-emulsied With a conventional propeller-type mixer for 2 minutes. The pre-emulsion is subsequently fed at a rate of 2 g.p.m. into a homogenizing device of the type shown in FIGS. 1 and 4 of the drawings and descrbed above.

A separate aqueous chain extender solution is then prepared by dissolving 191 gra'rns of dichloro-diaminodiphenyl methane in 20 parts of toluene and 40 parts of water. This mixture is heated to 70 C., agitated for 10 minutes with a conventional propeller-type agitator and then added for a period of several minutes to the prepolymer dispersion with agitation by a conventional propeller mixer during the addition. A mechanically stable polyurethane emulsion is formed.

EXAMPLE II A procedure substantially the same as Example I is employed with the exception that 97 grams of hexamethylene diamine is employed as a chain extender in lieu of dichlorodiamino diphenyl methane. The hexamethylene diamine is dissolved in 40 parts of water per 100 parts polymer before adding to the pre-emulsion. A mechanically stable polyurethane emulsion is formed.

EXAMPLE III (a) Prepolymer formation i750 grams of polyoxypropylene glycol of molecular weight laveraging 750 are added to 500 grams of diphenyl methane diisocyanate. The NCO/OH ratio is 2:1. The mixture is heated at 95 C. for 2 hours.

(b) `Chain extension 1,000 grams of the prepolymer are dissolved in 400 grams of toluene. This mixture along with 760 grams of aqueous surface active agent solution containing 7.9% by weight of the surface active agent consisting of dihydric polyoxyethylene-polyoxypropylenes having a molecular weight of about 16,000, a molecular weight of the polyoxypropylene base of -about 3,250 and a polyoxyethylene content of about 80% by weight are pre-emulsified as in Example I for 2 minutes. The pre-emulsion is subsequently fed through a homogenizer of the type shown in FIGS. 1 and 4 and described above, operating at 2 g.p.m. A separate aqueous chain extender solution is then prepared by dissolving 76 grams of 2methylpiper azine in 400 grams of water and agitating for 5 minutes with a commercial propeller-type agitator. This solution is added to the prepolymer dispersion with agitation by a conventional propeller-type mixer during the addition. A mechanically stable polyurethane emulsion is formed.

EXAMPLE IV A procedure substantially the same as that of Example III is employed with the exception that piperazine is employed as the chain extender instead of the Z-methylpiperazine. A mechanically stable polyurethane emulsion is formed.

EXAMPLE V The method of Example III is employed with the exception that the apparatus illustrated in FIGS. 5 and 6 is employed. A mechanically stable polyurethane emulsion is formed.

EXAMPLE VI A procedure substantially the same as 4Example III is employed with the exception that the apparatus illustrated in FIGS. 5 and 6 of the drawings is employed. A mechanically stable polyurethane emulsion is formed.

While there has been shown and described hereinabove the present preferred embodiments of this invention, it is to be understood that various changes, alterations and modilications can be m-ade thereto without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. An apparatus for dispersing a substance in a liquid comprising a housing having a chamber, an inlet and an outlet defined therein, and a series of plates arranged in succession in said chamber, each of said plates having a sharp edge orice extending therethrough, the orifice of one plate being out of alignment with the orifice of the next succeeding plate whereby a stream of fluid discharging through the orifice of a preceding plate impinges against an impervious impingement surface producing eddy currents in the stream of uid which is forced to change direction to pass through the orifice in the next succeeding plate, the distance between the orifice discharge and said impingement surface being at least about 11/2 times the smallest orifice dimension in a direction transverse to the fluid flow and not greater than about 1/2 the diameter of said inlet.

2. The apparatus of claim 1 wherein said orifices are elongated in a direction transverse to the direction of ow of a fluid passing through said orifice.

3. The apparatus of claim 1 wherein said impingement surface is flat.

4. 'Ihe apparatus of claim 3 wherein said orifices are elongated in a direction transverse to the direction ofv flow of a uid passing through said orifice.

5. The apparatus of claim 1 wherein said orifices are elongated in a direction transverse tothe direction of flow of a uid passing through said orifice and said impinge- -ment surface is wedge shape.

6. A process for dispersing a substance in a liquid comprising passing a mixture of said substance and said liquid through au `apparatus comprising a housing having a chamber, an inlet and an outlet defined therein, and a series of plates arranged in succession in said chamber, each of said plates having a sharp edge orifice extending therethrough, the orifice of one plate being out of alignment with the orifice of the next succeeding plate whereby a stream of fluid discharging through the orifice of a preceding plate impinges against an impervious impingement surface producing eddy currents in the stream of fluid which is forced to change direction to pass through the orice in the next succeeding plate, the distance between the orifice discharge and said impingement surface being at least about 11/2 times the smallest orifice dimension in a direction transverse to the fluid flow and not greater than about 1/2 the diameter of said inlet.

7. An apparatus for dispersing a substance in a liquid comprising a housing having a chamber, an inlet and an outlet defined therein, and a series of plates arranged in succession in said chamber, each of said plates having a sharp edge orifice extending therethrough, the orice of one plate being out of alignment with the orifice of the next succeeding plate whereby a stream of Huid discharging through the orifice of a preceding plate impinges against an impervious impingement surface producing eddy currents in the stream of fluid which is forced to change direction to pass through the orice in the next succeeding plate, said impingement surface being in the form of a projection having side surfaces which converge upon each other, the distance between the orifice discharge and said impingement surface being not greater than about 1/2 the diameter of said inlet.

References Cited UNITED STATES PATENTS 1,947,929 2/ 1934 Emanueli 13S-42 2,693,391 11/1954 Manseau 259-4 XR 2,965,695 12/ 1960 Sleicher 259-4 XR 2,988,151 `6/ 1961 Dion-Biro 259-4 XR 3,001,771 9/1961 Pro 259-4 XR 3,266,780 8/ 1966 Waters 259-4 ROBERT W. JENKINS, Primary Examiner 

